- ID:
- ivo://CDS.VizieR/J/A+A/403/1105
- Title:
- Extremely metal-poor giants equivalent widths
- Short Name:
- J/A+A/403/1105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports detailed abundance analyses for four extremely metal-poor (XMP) giant stars with [Fe/H]<-3.8, based on high-resolution, high- S/N spectra from the ESO VLT (Kueyen/UVES) and LTE model atmosphere calculations. The derived [{alpha}/Fe] ratios in our sample exhibit a small dispersion, confirming previous findings in the literature, i.e. a constant overabundance of the {alpha}-elements with a very small (if any) dependence on [Fe/H]. In particular, the very small scatter we determine for [Si/Fe] suggests that this element shows a constant overabundance at very low metallicity, a conclusion which could not have been derived from the widely scattered [Si/Fe] values reported in the literature for less metal-poor stars. For the iron-peak elements, our precise abundances for the four XMP stars in our sample confirm the decreasing trend of Cr and Mn with decreasing [Fe/H], as well as the increasing trend for Co and the absence of any trend for Sc and Ni. In contrast to the significant spread of the ratios [Sr/Fe] and [Ba/Fe], we find [Sr/Ba] in our sample to be roughly solar, with a much lower dispersion than previously found for stars in the range -3.5<[Fe/H]<-2.5.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/434/1681
- Title:
- Extremely metal-poor stars CaII triplet
- Short Name:
- J/MNRAS/434/1681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extend our previous calibration of the infrared CaII triplet (CaT) as a metallicity indicator to the metal-poor regime by including observations of 55 field stars with [Fe/H] down to -4.0dex. While we previously solved the saturation at high metallicity using a combination of a Lorentzian and a Gaussian to reproduce the line profiles, in this paper we address the non-linearity at low metallicity following the suggestion of Starkenburg et al. of adding two non-linear terms to the relation among the [Fe/H], luminosity and strength of the calcium triplet lines. Our calibration thus extends from -4.0 to +0.5 in metallicity and is presented using four different luminosity indicators: V-V_HB_, M_V_, M_I_ and M_K_. The calibration obtained in this paper results in a tight correlation between [Fe/H] abundances measured from high-resolution spectra and [Fe/H] values derived from the CaT, over the whole metallicity range covered.
- ID:
- ivo://CDS.VizieR/J/A+A/501/519
- Title:
- Extremely metal-poor turnoff stars abundances
- Short Name:
- J/A+A/501/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detailed chemical abundances of extremely metal-poor (EMP) stars are key guides to understanding the early chemical evolution of the Galaxy. Most existing data, however, treat giant stars that may have experienced internal mixing later. We aim to compare the results for giants with new, accurate abundances for all observable elements in 18 EMP turnoff stars. VLT/UVES spectra at ~45000 and S/N ~130 per pixel (330-1000nm) are analysed with OSMARCS model atmospheres and the TURBOSPECTRUM code to derive abundances for C, Mg, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, and Ba. For Ca, Ni, Sr, and Ba, we find excellent consistency with our earlier sample of EMP giants, at all metallicities. However, our abundances of C, Sc, Ti, Cr, Mn and Co are ~0.2dex larger than in giants of similar metallicity. Mg and Si abundances are ~0.2dex lower (the giant [Mg/Fe] values are slightly revised), while Zn is again ~0.4dex higher than in giants of similar [Fe/H] (6 stars only). For C, the dwarf/giant discrepancy could possibly have an astrophysical cause, but for the other elements it must arise from shortcomings in the analysis. Approximate computations of granulation (3D) effects yield smaller corrections for giants than for dwarfs, but suggest that this is an unlikely explanation, except perhaps for C, Cr, and Mn. NLTE computations for Na and Al provide consistent abundances between dwarfs and giants, unlike the LTE results, and would be highly desirable for the other discrepant elements as well. Meanwhile, we recommend using the giant abundances as reference data for Galactic chemical evolution models.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/3431
- Title:
- Extremely red quasars in BOSS
- Short Name:
- J/MNRAS/464/3431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual 'wingless' line profiles, large NV/Ly{alpha}, NV/CIV, SiIV/CIV and other flux ratios, and very broad and blueshifted [OIII] {lambda}5007. Here we present a new catalogue of CIV and NV emission-line data for 216188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR colour, secondarily on REW(CIV), and not at all on luminosity or the Baldwin Effect. We identify a 'core' sample of 97 ERQs with nearly uniform peculiar properties selected via i-W3>=4.6(AB) and REW(CIV)>=100{AA} at redshifts 2.0-3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity <logL(ergs/s)>~47.1, sky density 0.010deg^-2^, surprisingly flat/blue UV spectra given their red UV-to-mid-IR colours, and common outflow signatures including BALs or BAL-like features and large CIV emission-line blueshifts. Their SEDs and line properties are inconsistent with normal quasars behind a dust reddening screen. We argue that the core ERQs are a unique obscured quasar population with extreme physical conditions related to powerful outflows across the line-forming regions. Patchy obscuration by small dusty clouds could produce the observed UV extinctions without substantial UV reddening.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/83
- Title:
- 22 extreme [OIII] emitters at z~0.5 from SDSS-DR14
- Short Name:
- J/ApJ/860/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have found a sample of extreme emission-line galaxies (EELGs) with strong [OIII]{lambda}5007 emission at z~0.5. Using broadband photometric selection and requiring small uncertainties in photometry, we searched the 14th Data Release of the Sloan Digital Sky Survey (SDSS) and found 2658 candidates with strong i-band excess (i-z<=r-i-0.7). We further obtained 649 SDSS spectra of these objects, and visually identified 22 [OIII] emitters lying at 0.40<z<0.63. Having constructed their ultraviolet-infrared spectral energy distributions, we found that they have fairly blue r-W2 and red W1-W4 colors, indicative of strong, warm dust emission. Their rest-frame [OIII]{lambda}5007 equivalent widths are mostly 200-600{AA}, and their high [OIII]{lambda}5007/H{beta} ratios put them at the boundary of star-forming galaxies and active galactic nuclei on line ratio classification diagrams. The typical E(B-V) and electron temperature of [OIII] emitters are ~0.1-0.3mag and ~104K, respectively. The lowest metallicity of our [OIII] emitters with S/N[OIII]{lambda}4363>3 is 12+log(O/H)=7.98_-0.02_^+0.12^, with a median value of 8.24_-0.04_^+0.05^. Our [OIII] emitters exhibit remarkably high line luminosity-18/22 have L[OIII]{lambda}5007>5x10^42^erg/s and 5/22 have L[OIII]{lambda}5007>10^43^erg/s. Their estimated volume number density at z~0.5 is ~2x10^-8^Mpc^-3^, with L[OIII]{lambda}5007 down to ~3x10^42^erg/s. The cumulative number distribution of EELGs across different redshifts is indicative of a strong redshift evolution at the bright end of the [OIII] luminosity function.
- ID:
- ivo://CDS.VizieR/J/AJ/124/1283
- Title:
- Faint Markarian galaxies of SBS. III.
- Short Name:
- J/AJ/124/1283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We continue our program of spectroscopic observations of objects from the Second Byurakan Survey (SBS). This survey contains more than 3600 objects with m_pg_<19.5mag, half of them being galaxies and the other half being starlike objects. The aim of this work is to compile a complete sample of faint (B<17) Markarian galaxies. Here we present spectroscopic data for 185 galaxies, obtained with the 6m telescope of the Special Astrophysical Observatory in Russia and the 2.1m telescope of the Guillermo Haro Astrophysical Observatory in Mexico. In the present subsample, we find three new Seyfert 1 galaxies (SBS 0654+598, 1118+541, and 1320+551); one narrow-line Seyfert 1 (SBS 0748+499), one Seyfert 2 (SBS 0925+585), and three Seyfert2/LINER (SBS 0811+584, 1344+527, and 1428+529) galaxies; 12 LINERs; 13 blue compact dwarf galaxies; 65 starburst nuclei; 85 emission-line galaxies; and two absorption galaxies. Relevant astrophysical parameters (magnitude, redshift, relative intensities of emission lines, etc.) are given for the observed galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/158/157
- Title:
- Fairly bright slow rotators chemical compositions
- Short Name:
- J/AJ/158/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a detailed abundance study of the fairly bright slow rotators HD 30085 (A0 IV), HD 30963 (B9 III), and HD 174567 (A0 V), hitherto reported as normal stars and the sharp-lined {chi} Lupi A (B9 IV HgMn). In the spectra of HD 30085 and HD 30963, the Hg II line at 3984 {AA} is conspicuous and numerous lines of silicon, manganese, chromium, titanium, iron, strontium, yttrium, and zirconium appear to be strong absorbers. A comparison of the mean spectra of HD 30085 and HD 30963 with a grid of synthetic spectra for selected unblended lines having reliable updated atomic data reveals large overabundances of phosphorus, titanium, chromium, manganese, strontium, yttrium, zirconium, barium, platinum, and mercury, and underabundances of helium, magnesium, scandium, and nickel. The surface abundances of {chi} Lupi A have been rederived on the same effective temperature scale and using the same atomic data for consistency and comparison for HD 30085 and HD 30963. For HD 174567, milder deficiencies and excesses are found. The abundances of sodium, magnesium, and calcium have been corrected for non-LTE (NLTE) effects. The effective temperatures, surface gravities, low projected rotational velocities, and the peculiar abundance patterns of HD 30085 and HD 30963 show that these stars are two new HgMn stars and should be reclassified as such. HD 174567 is most likely a new marginally chemically peculiar star. A list of the identifications of lines absorbing more than 2% in the spectrum of HD 30085 is also provided.
- ID:
- ivo://CDS.VizieR/J/MNRAS/407/465
- Title:
- Fast-rotating M dwarfs in NGC2516
- Short Name:
- J/MNRAS/407/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report radial velocities (RVs), projected equatorial velocities (vsini) and CaII triplet (CaT) chromospheric activity indices for 237 late-K to mid-M candidate members of the young open cluster NGC 2516. These stars have published rotation periods between 0.1 and 15d. Intermediate-resolution spectra were obtained using the Giraffe spectrograph at the Very Large Telescope. Membership was confirmed on the basis of their RVs for 210 targets.
- ID:
- ivo://CDS.VizieR/J/A+A/384/491
- Title:
- Fast-rotating nearby solar-type stars. I.
- Short Name:
- J/A+A/384/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of high-resolution spectroscopic and high-precision photometric observations on a sample of 129 late-F and G-type nearby stars selected on the basis of their large rotational velocity. Using also data from the Hipparcos satellite, CORAVEL and from the ROSAT satellite database, we infer spectral types, compute radial velocities, vsini, Li abundances and X-ray luminosities and investigate the single or binary nature of the sample stars. Such a careful analysis of our sample shows a large fraction of binaries (~62%) and of young single disk stars. In particular, at least 9 stars can be considered bona-fide PMS or ZAMS objects, and 30 stars are identified as SBs for the first time. Information on the presence of Ca II K emission and on optical variability is given for some of the stars of the sample. The photometry has been obtained at the European Southern Observatory (ESO-La silla, Chile) during several observing runs (19/11-03/12 1993, 24/11-04/12 1994, 15-28/01/1995 and 1-12/10/1995), by using the 50cm ESO telescope. The figures were published in paper II.
- ID:
- ivo://CDS.VizieR/J/ApJS/189/15
- Title:
- FeII emission in a sample of AGN spectra
- Short Name:
- J/ApJS/189/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of optical FeII emission in 302 active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. We group the strongest FeII multiplets into three groups according to the lower term of the transition (b^4^F, a^6^S, and a^4^G terms). These approximately correspond to the blue, central, and red parts, respectively, of the "iron shelf" around H{beta}. We calculate an FeII template that takes into account transitions into these three terms and an additional group of lines, based on a reconstruction of the spectrum of I Zw 1. This FeII template gives a more precise fit of the FeII lines in broad-line AGNs than other templates. We extract FeII, H{alpha}, H{beta}, [OIII], and [NII] emission parameters and investigate correlations between them. We find that FeII lines probably originate in an intermediate line region. We note that the blue, red, and central parts of the iron shelf have different relative intensities in different objects. Their ratios depend on continuum luminosity, FWHM H{beta}, the velocity shift of FeII, and the H{alpha}/H{beta} flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of FeII and [OIII] on continuum luminosity. We find that there is a Baldwin effect for [OIII] but an inverse Baldwin effect for the FeII emission. The [OIII]/FeII ratio thus decreases with L_{lambda}5100_. Since the ratio is a major component of the Boroson & Green Eigenvector 1 (EV1), this implies a connection between the Baldwin effect and EV1 and could be connected with AGN evolution. We find that spectra are different for H{beta} FWHMs greater and less than ~3000km/s, and that there are different correlation coefficients between the parameters.
